Stencils for use in conjunction with a substrate such as a business form have been used for many years. It is a huge market as approximately 80% of industry uses stencils.
The stencil material generally consists of a thin tissue material with a top and a bottom surface. A carbon layer is often incorporated into the bottom surface of the stencil. The carbon layer allows an impression of indicia on the top surface of the stencil to be transferred to a substrate. The transfer allows the impressed indicia to be readable on the substrate as well as the stencil itself.
The stencil material with the impressed indicia is removed from the substrate and taken to a second surface. The impressed indicia are reproduced on this second surface by applying a fluid medium, usually an ink, to the top surface of the stencil material. The fluid medium passes through the stencil material by way of the impressed indicia and thereby reproduces the impressed indicia on the second surface.
For example, the original substrate is often a document such as a bill of lading or an invoice while the second surface is a package being shipped which corresponds to such a document. Such use of stencil materials reduces the chance of a typographical error in transcribing an address as well as being a real time-saver by eliminating the need to write the shipping address on a label or directly on each separate package. In a multi-package shipment, the errors are reduced even more and the material and time saved even greater as a single stencil can be used for multiple packages.
Two somewhat conflicting concerns have bedeviled the stencil industry. On one hand, the shipping floor wants a stencil that is tough enough to take rough handling. Conversely, the office wants a product which can be attached and removed from a form quickly and easily without jamming the printing equipment.
Originally, in the office the stencil material was directly laid on the substrate, usually some type of business form. Sometimes adhesive tape was used to hold the material in place. This proved unsatisfactory as the thin stencil material tended to fold over and tear when placed in typewriters or printers. In addition, this method was labor-intensive as well as being time consuming.
An edge made of heavier material which attaches to the substrate was added to solve some of these problems. The stencil material was attached to the edge thus forming a tape top stencil. The edge was attached to the substrate and provided support for the stencil material. Perforations between the edge and the stencil material were added to simplify their separation.
While an improvement, the edge did not totally solve the problem of tearing and folding. The thin stencil material was still unsupported along three sides. Therefore, often a releasable glue was applied to attach the free sides to prevent jamming. As a consequence, applying tape top stencils to a form is still a slow, tedious process.
In addition, little if any gains were seen in productivity in the office because the glue could not coat to the edges of the stencil. As a result, printer jamming still was a common occurrence. Handling the separated stencil, for example, by warehousemen as noted above, was still a considerable problem. Also, the edge was generally left behind on the substrate which added its own set of problems. The edge made each substrate thicker which resulted in using up valuable storage space.
One development which aided the shipping floor handling concerns was the framed stencil in which a frame of heavier construction completely covers the periphery of the stencil material. Once detached from the substrate, the frame prevented the folding and tearing of the stencil material. The stencil material was held rigidly, thus making the application of a fluid medium or reading the impressed indicia easier.
However, many drawbacks still exist with the framed stencil as described. For example, if the frame stencil is not adhered to the substrate completely, the stiff frame will separate from the substrate when traversing rollers in a printer which acts to jam the printer. Another drawback is the limitations imposed by the equipment needed to affix the framed stencil to the substrate.
Both frame stencils and tape top stencils are generally adhered to substrate by the application of a releasable adhesive between the frame and the form. Presently, this requires the addition of a releasable glue between the form and the stencil which adds considerably to the cost and time required to apply the stencil to the substrate. The glue application machinery is very expensive and slow. Quite often, users will apply the glue manually to avoid the expense of such a machine.
In addition, once the stencil is removed from the substrate, a glue residue is left on both the stencil and the substrate. Carbon will adhere to the glue and produce smears on the form. The adhered carbon is aesthetically displeasing at best and can render the form unreadable. The substrates can stick together if stacked and will pick up dirt and dust which adhere to the glue residue. Also, when the stencil is placed on the second surface, such glue residue may cause the stencil to adhere to the second surface.
Further, the amount of glue applied is a critical factor which is difficult to control. If the amount of glue is excessive, the stencil may not release from the substrate. If the amount of glue is inadequate, the stencil may release from the substrate prematurely thus jamming the printer.
In addition to the problem of controlling the amount of glue applied to the stencil, the location of the glue is also important. The glue can not extend beyond the stencil in order to prevent stacked substrates from adhering to one another. As a result, the glue cannot totally seal the edges of the stencil which results in exposed dry edges. Such exposed dry edges are very susceptible to jamming in machines such as printers or typewriters.
The aforementioned problems have made the affixation of stencils to substrates a very slow, expensive and complex process with severe limitations. For example, the benefits of framed stencils are often negated by problems in affixing such stencils to forms and therefore the majority of stencils in use today are the tape top stencils described earlier.
The industry has sought to correct these problems for a number of years. One desired approach has been to find a method of affixing stencils to forms which utilizes label affixing equipment. Label affixing equipment is easy to operate, far less expensive, much faster and far more accurate than a conventional glue machine. However, to utilize such equipment, the stencils must be produced in a format on a roll. In short, label affixing equipment requires a stencil apparatus which is specifically designed for use on such equipment.
Accordingly, what is needed is a stencil apparatus which is releasably attached to a substrate but avoids leaving any objectionable residues on the substrate once the framed stencil is removed. Such a stencil apparatus should also retain the considerable advantages entailed by the use of framed stencils. The apparatus should also allow for the easy gripping and removal of the stencil from the substrate but also alleviate the problem of printer jams. Further, the apparatus must be producible in a roll which is suitable for use on label affixing equipment. The present invention meets these desires.